<div class="loading full" *ngIf="!errorMessage">
  <div class="textcenter">
    正在加载设备...
  </div>
</div>
<div class="full" *ngIf="errorMessage">
  <div>
    <img src="./assets/img/device-loading-error.png">
  </div>
  <div class="textcenter">
    {{errorMessage}}
  </div>
</div>